The invention concerns a device for reducing rotary vibrations on transmission of a drive power which may be provided by an internal combustion engine in the motor vehicle. A rotary vibration reduction device according to the preamble is known from the prior art, in particular as a dual mass flywheel from DE 8713332 U1.
The invention is described below with reference to a drivetrain for a motor vehicle with an internal combustion engine working on the reciprocating piston principle, but this should not be regarded as a restriction of the invention to such an embodiment. Internal combustion engines working on the reciprocating piston principle, because of their design, have an uneven drive torque, i.e. the torque which can be output by such an engine is loaded with rotary vibrations or rotational irregularities which often detract from the driving comfort of a motor vehicle.
The drive torque provided by such a drive machine may be considered as a mean torque which is overlaid by rotational irregularities in the form of a vibration. Such rotary vibrations or rotational irregularities are primarily transmitted to the drivetrain and perceived as uncomfortable by the vehicle occupants. In the prior art, there are numerous devices for reducing such rotary vibrations. In this context, so-called dual mass flywheels (ZMS) are of primary importance. In these, a primary connector may be coupled to the internal combustion engine and a secondary connector may be coupled to the further drivetrain. The two connectors can be connected together via a spring device or a spring and damper device. A rotary vibration provokes a rotational movement of the primary connector relative to the secondary connector, wherein these rotary vibrations are firstly reduced by the vibratable sprung mass system, and also can be damped and hence further reduced by the damper device.
DE8713332U1 deals with a dual mass flywheel for a drive system of a motor vehicle consisting of a first rotary mass attached to the crankshaft of the internal combustion engine, a second rotary mass connected to the gearbox input components and mounted rotationally on the first rotary mass, and a torsion damping device between the two rotary masses for damping torsional vibrations. In general, such a system is also known from DE 3411092 A1.
It is an object of the invention to specify an improved device for reducing rotary vibrations.
A rotary vibration reduction device in the sense of the invention means a device for a motor vehicle which is configured to transmit a drive power, in the form of a torque and a rotation speed, from a drive machine to a drivetrain. The rotary vibration reduction device is provided in particular for use with an internal combustion engine working on the reciprocating piston principle. Further preferably, this is configured as a hydraulic device and, since the fluids normally used in such a device are incompressible, preferably includes a device which has a spring stiffness or an elasticity in order to form a vibratable system. In a particularly preferred embodiment of the invention, brake fluid is used as the fluid since this is particularly stable against pressure and temperature.
In the sense of the invention, the drivetrain to which the drive power transmissible via the rotary vibration reduction device is output by the drive machine, is understood to be a shaft or a gearbox or another component which is designed to transmit this drive power in the direction of at least one drivable wheel of a motor vehicle.
In the sense of the invention, a primary connector of the rotary vibration reduction device is the portion of this device to which the drive torque from the internal combustion engine can be transmitted. Preferably, the primary connector can be connected to a crankshaft of the internal combustion engine, further preferably can be connected rotationally fixedly thereto, preferably directly thereto.
In the sense of the invention, a secondary connector of the rotary vibration reduction device is a portion thereof which is firstly configured to transmit to the drivetrain the drive power which is transmitted from the internal combustion engine to the rotary vibration reduction device, and secondly the secondary connector is mounted rotatably relative to the primary connector, in particular through a specific angular range, preferably of less than 360°. Further preferably, the secondary connector can be connected to a clutch for selective transmission of the drive power to a gearbox, preferably with a start-up clutch or preferably with a torque converter.
Here, the primary connector can be connected to the secondary connector by a coupling device, in particular can be connected such that the drive power can be transmitted from the primary connector to the secondary connector, in particular in the form of a torque and a rotation speed. Further preferably, the primary connector and the secondary connector are arranged coaxially to each other and, to transmit the drive power, rotate about a common main axis, in particular about the same axis about which the crankshaft of the internal combustion engine also rotates. In relation to the transmission of drive power, the coupling device is thus arranged between the primary and secondary connectors.
The coupling device preferably includes a vibration reduction actuator with a piston chamber and a piston element which is movable in said piston chamber. Here, the piston element may be loaded with a working pressure in the piston chamber in order to generate a reduction force. Figuratively, the vibration reduction actuator is preferably configured as a gas pressure actuator or a gas pressure cylinder, or preferably as a hydraulic actuator or hydraulic cylinder. Preferably, the piston chamber and piston element can be coupled with the primary and secondary connectors such that a rotational movement of the primary connector relative to the secondary connector generates a displacement of the piston element in the piston chamber. Further preferably, with such a connection a rotational irregularity imposed on the primary connector can be reduced by the coupling device, in particular by a corresponding control of the working pressure. Preferably, the vibration reduction actuator has a partially or completely arcuate form.
Here, this movement of the primary connector relative to the secondary connector is achieved against the reduction force generated by the working pressure in the piston chamber. Advantageously, the working pressure in the piston chamber can be controlled by a pressure-generating device, and hence via this the reduction force is controllable. Further preferably, the reduction force is selected such that the quasi-statically transmissible drive torque (mean torque or torque without superposition of rotational irregularities) can be transmitted without a twist of the primary connector relative to the secondary connector. In contrast, in a conventional system, for example a ZMS, this drive torque would lead to a preload on the bow springs and hence to a twist of a primary mass of such a ZMS relative to its secondary mass.
With the proposed device, it is thus possible to set the reduction force within a wide range. In particular, it is thus possible to achieve a particularly high extent of vibration reduction.
In a preferred embodiment, the piston chamber can be filled by a hydraulic fluid, preferably with an incompressible fluid. Further preferably with an oil, in particular a hydraulic oil and preferably with brake fluid. In this embodiment, the vibration reduction actuator is configured as a hydraulic actuator, preferably with a circular piston face and particularly preferably with a cylindrical form of the piston chamber. In particular with such a fluid, which is not compressible or only slightly compressible, a particularly good controllability of the system can be achieved.
In a further preferred embodiment, the vibration reduction actuator is a device which can be filled with a gas as the working medium, preferably a gas pressure cylinder, and preferably its piston chamber can be filled with a gas. Such a gas may in particular be air. In particular, by means of a gas pressure cylinder, the rotary vibration reduction device can be constructed particularly simply.
In a preferred embodiment, the pressure-generating device is formed as a hydraulic or pneumatic device for providing a working pressure. Preferably, such a device may be filled with a hydraulic medium for generating the working pressure. Preferably, the pressure-generating device may be or is connected fluid-conductively to the piston chamber of the vibration reduction actuator. Further preferably, the pressure-generating device is formed in the same way as the vibration reduction actuator, i.e. either both are formed as hydraulic or as gas pressure devices. Further preferably, the two devices are configured as different types, i.e. one is a gas pressure device and the other a hydraulic device.
In a preferred embodiment, the rotary vibration reduction device includes a pressure-balancing device. Preferably, the pressure-balancing device is a preloadable pressure accumulator; in particular, this is a spring since this introduces an elasticity into the system. Further preferably, the pressure-balancing system includes a mechanical spring, preferably a gas spring, or preferably a device with a solid-body spring, in particular a metal spring, preferably a steel spring or an elastomer spring, or a combination of several of said springs. Preferably, the pressure-balancing device is a hydraulic spring; since a hydraulic fluid which may be received therein is usually incompressible, this can be combined with a spring element of the type cited above. Such embodiments of a pressure-balancing device are known from the prior art and particularly reliable in function.
According to a preferred basic concept, by the combination of a vibration reduction actuator for coupling the primary and secondary connectors, a pressure-generating device for setting the working pressure, and a pressure-balancing device for providing a spring rate, it is possible to achieve an advantageous vibration reduction. The working pressure is here set as a function of a mean torque to be transmitted, such that as a result, effectively no twist, or no substantial twist, occurs of the secondary connector relative to the primary connector because of this torque. If rotary vibrations are superposed over the mean torque, i.e. a torque irregularity, as is inherent in the system with an internal combustion engine working on the reciprocating piston principle, the pressure-balancing device is excited to vibrate and hence these irregularities are transmitted at least incompletely to the secondary connector, and hence a vibrational decoupling of the secondary connector from the primary connector can be achieved.
Further preferably, the pressure-balancing device may be connected fluid-conductively to the pressure-generating device. In particular, using the pressure-balancing device a working pressure may be applied so that with the pressure-generating device, pressure fluctuations can be damped which are induced by the rotational irregularities which may be imposed on the primary connector. In particular, due to the fluid-conductive connection of the pressure-generating and pressure-balancing devices, the pressure-balancing device is preloaded with the working pressure. The working pressure applied by the pressure-generating device can be provided with particularly little energy since only a small volume flow is moved, and hence a particularly efficient operation of the rotary vibration reduction device is possible.
In a preferred embodiment, the rotary vibration reduction device, in particular the coupling device, includes a further piston chamber. Further preferably, a further piston element can be moved in the further piston chamber. Further preferably, the further piston element seals the further piston chamber fluid-tightly against the piston chamber and can preferably be connected to the piston element, particularly preferably is produced integrally therewith. By such a configuration with such a further piston chamber, the vibration reduction actuator preferably has the form of an actuator, preferably a cylinder with two piston chambers between which the preferably connected piston element can move to and fro. To transmit a drive torque, the preferably connected piston element is displaced in the direction of one of the piston chambers, wherein this displacement tendency is countered by different working pressures in the piston chamber and in the further piston chamber. With the proposed embodiment, a rotary vibration reduction device is created in which the preferably connected piston element is clamped hydraulically between the piston chambers, and hence a particularly good controllability can be achieved.
In a further preferred embodiment, the rotary vibration reduction device, which in particular has a vibration reduction actuator with two piston chambers, includes a further pressure-generating device. Using this further pressure-generating device, in particular the further working pressure in the further piston chamber can be modified. Preferably, the further pressure-generating device is configured in the same way as the pressure-generating device.
In a preferred embodiment, the rotary vibration reduction device includes a further pressure-balancing device which may be connected fluid-conductively to the further pressure-generating device. Here, the further pressure-balancing device is a pressure-balancing device of the type described above and may have the same structure as or a different structure from the said pressure-balancing device.
In a preferred embodiment of the rotary vibration reduction device, in the torque transmission direction from the primary connector to the secondary connector, a spring device is arranged between these connectors. Preferably, the spring device is configured as a gas pressure spring device and preferably as a mechanical spring device with a solid-body spring. Preferably, this spring device has a steel spring or an elastomer spring as a spring element. Preferably, the spring device is arranged such that a spring force can be transmitted from the primary connector to the secondary connector. Further preferably, the spring device is arranged such that a change in this spring force can be provoked by a rotational movement of the primary connector relative to the secondary connector. In particular, using such a spring device, a particularly effective reduction of rotary vibrations can be achieved.
In a preferred embodiment, the vibration reduction actuator is arranged such that a cylinder force can be transmitted from the primary connector to the secondary connector. Preferably, this spring device and the vibration reduction actuator are connected together in series and mechanically, i.e. in relation to the forces which can be transmitted thereby. In particular in a static load case therefore, the spring force and the cylinder force are equal. In particular, because of the serial arrangement of the spring device and the vibration reduction actuator, it can be achieved that the primary connector can execute a particularly wide travel in relation to the secondary connector, or has a range with a first spring stiffness (spring device) and with a second spring stiffness (pressure-balancing device), and hence a soft damping of the rotary vibrations can be achieved.
In a preferred embodiment of the invention, the spring device and the vibration reduction actuator are connected together in parallel and mechanically, i.e. in relation to the forces they can transmit. With a parallel connection of the spring device and the vibration reduction actuator, the total forces they can transmit between the primary connector and the secondary connector are the sum of the individual forces. In particular, using such an arrangement, particularly high forces can be transmitted between the primary connector and the secondary connector, and particularly simple dimensioning of the vibration reduction actuator is possible.
In a preferred embodiment, the rotary vibration reduction device includes a decoupling device with a decoupling cylinder. Preferably, the decoupling cylinder includes a decoupler piston, a primary decoupler piston chamber and preferably a secondary decoupler piston chamber. Preferably, the decoupler piston is movable in the primary decoupler piston chamber. Preferably, the two decoupler piston chambers are separated from each other fluid-tightly by the decoupler piston. Further preferably, the pressure-generating device, or the further pressure-generating device or both, may be connected fluid-conductively to the primary decoupler piston chamber. Preferably, the secondary decoupler piston chamber may be connected fluid-conductively to the piston chamber or the further piston chamber. Preferably, the decoupler cylinder is thus configured as a hydraulic cylinder or as a gas pressure cylinder, wherein the term “cylinder” in this context should be understood in particular not as a geometric description but as a generally common description of such actuators. Further preferably, at least one or both decoupler piston chambers are also configured geometrically as cylinders. In particular, by means of such a decoupling device, a further pressure fluctuation may be applied to the coupling device, and in particular thus the rotational irregularities transmitted can be further reduced.
Further preferably, the decoupling device has a decoupling actuator, by which a force may be applied to the decoupler piston. Preferably, the decoupler piston may be excited by the decoupling actuator with a vibration which is preferably in contraphase to the rotary vibrations acting on the primary connector. Using such a contraphase vibration, the rotary vibrations which can be transmitted from the primary connector to the secondary connector are actively reduced. Preferably, the decoupling actuator is configured as an electromechanical actuator, further preferably as a hydraulic or pneumatic actuator. In particular, using such a decoupling device, an improved controllability of the rotary vibration reduction device can be achieved.
In a preferred embodiment of the invention, the pressure-generating device, or the further pressure-generating device or both, is arranged at one of the connectors (primary connector, secondary connector) or at least may be kinematically coupled to one of these. In particular, by this arrangement, the pressure-generating device, or the further pressure-generating device or both, thus rotates with one of the connectors on power transmission. In particular, using such an embodiment of the invention, it is possible that no pressurized media need be transmitted to the rotating connectors.
In a preferred embodiment, the rotary vibration reduction device includes an actuator with recuperation capacity. An actuator with recuperation capacity in the sense of the invention means an actuator for conversion of an alternating motion or a pressure fluctuation into preferably hydrostatic or preferably electrical energy. Preferably, this energy can be stored in an intermediate store, preferably an electrochemical or electrostatic accumulator, or in a pressure accumulator, and returned to the rotary vibration reduction device for its operation.
Preferably, the coupling device includes an actuator with recuperation capacity, preferably the vibration reduction cylinder is configured as or may be connected to an actuator with recuperation capacity. Further preferably, the pressure-generating devices, preferably the pressure-balancing device and particularly preferably the decoupler device, include such an actuator with recuperation capacity. In particular, using an actuator with recuperation capacity, the energy needs of the rotary vibration reduction device can be lowered and hence its particularly efficient operation is possible.
In a preferred embodiment of the invention, the pressure-generating device, or the further pressure-generating device or both, is arranged stationarily in relation to the rotational movement of the connectors (primary connector, secondary connector). Preferably, at least one of these two devices (pressure-generating device, further pressure-generating device) is arranged stationarily on a carrier element of a motor vehicle in which the rotary vibration reduction device is arranged. In particular, with such embodiments, the connectors rotate relative to at least one of the pressure-generating devices on transmission of the drive power.
To operate the rotary vibration reduction device, it is preferably provided that the rotational movement of the primary connector is detected, preferably the rotation speed is measured by at least one sensor, further preferably an angular acceleration is measured or derived from this rotational movement. Further preferably, an acceleration sensor is mounted on the rotary vibration reduction device in order to detect an angular acceleration, preferably of the primary connector or of the secondary connector or both.
To operate the rotary vibration reduction device, it is preferably furthermore provided that the rotational movement of the secondary connector is detected, preferably the rotation speed is measured by at least one sensor, further preferably an angular acceleration is measured or derived from this rotational movement.
Preferably, individual or all established values of the detected rotational movements are supplied to a calculating unit, which uses these rotational movements to control the working pressure in the piston chamber of the vibration reduction actuator or decoupling device or both. Further preferably, the working pressure is regulated such that the angular acceleration of the secondary connector is less than the angular acceleration of the primary connector. In particular, using a slight angular acceleration of the secondary connector, a particularly comfortable driving operation is possible.
A further method for controlling the rotary vibration reduction device is provided for starting a motor vehicle with an internal combustion engine and such a device, i.e. for starting the internal combustion engine in combustion mode. In particular, such a method is used for a so-called direct start, wherein direct start here means in particular that the starting of the internal combustion engine after it has been switched off to a precise position and a combustible fuel and air mixture is present in a combustion chamber. To start the internal combustion engine, the fuel and air mixture is now ignited and this start pulse is sufficiently large to operate the internal combustion engine further in combustion mode.
With conventional dual mass flywheels, it is possible that the start pulse is damped by the dual mass flywheel and operation in combustion mode is not therefore possible.
In the proposed method, preferably for direct start, the working pressure is increased to a threshold value which can be determined depending on the internal combustion engine and the drivetrain, and hence a stiffer coupling of the primary connector to the secondary connector is achieved than in normal operation, i.e. if the rotary vibration reduction device were operated in driving modes of the motor vehicle. In particular, due to this rotationally stiff coupling of the primary connector to the secondary connector, the start pulse of the internal combustion engine is not damped and its operation in combustion mode is possible.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.